Abstract

We study B±→J/ψπ± and B±→J/ψK± decays in a sample of about 89×106 BB̅ pairs collected with the BABAR detector at the PEP-II asymmetric B factory at SLAC. We observe a signal of 244±20 B±→J/ψπ± events and determine the ratio B(B±→J/ψπ±)/B(B±→J/ψK±) to be [5.37±0.45(stat)±0.11(syst)]%. The charge asymmetries for the B±→J/ψπ± and B±→J/ψK± decays are determined to be Aπ=0.123±0.085(stat)±0.004(syst) and AK=0.030±0.015(stat)±0.006(syst), respectively.